Three-dimensional range camera

• US 4,687,325 A
• Filed: 03/28/1985
• Issued: 08/18/1987
• Est. Priority Date: 03/28/1985
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Corby, Nelson R. Jr.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/717,367
• Time in Patent Office: 873 Days
• Field of Search: 356/1, 356/2, 356/4, 356/5, 356/141, 356/152, 358/98, 358/108, 358/125
• US Class Current: 356/3.09
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50

Abstract

A non-contact sensor system measures distance from a reference plane to many remote points on the surface of an object. The set of points at which range is measured lie along a straight line (N points) or are distributed over a rectangular plane (M×N points). The system is comprised of a pattern generator to produce a 1×N array of time/space coded light rays, optionally a means such as a rotating mirror to sweep the coded light rays orthogonally by steps, a linear array camera to image subsets of the light rays incident on the object surface, and a high speed range processor to determine depth by analyzing one-dimensional scan signals. The range camera output is a one-dimensional profile or a two-dimensional area range map, typically for inspection and robotic vision applications.

Claims

1. A non-contact sensor system to measure range to an object from a reference plane comprising:

a pattern generator and projector to produce a 1×

N array of time and space coded light rays whose intensities can each be varied with time, and to project P sequential presentations of different light ray patterns onto a three-dimensional object, where P=1+log_b N, b is the number of brightness levels and N is the number of rays;

a linear array sensor which views, at an angle to projected light rays, points of light where said rays are incident on the surface of said object, and generates one-dimensional scan signals which have ray peaks at locations corresponding to imaged light; and

a range profile processor to analyze said scan signals to uniquely identify all rays, determine depth from the displacement of said ray peaks from calibration, reference plane peaks, and provide a range map.

2. The system of claim 1 and means for orthogonally sweeping said 1×

N array of coded light rays by steps over a rectangular plane, whereby at each step one line of light points on the surface of said object are imaged by said linear array sensor and depth is measured to provide an area range map.

3. The system of claim 2 wherein said orthogonal sweep means is a rotating mirror.

4. The system of claim 1 wherein said pattern generator includes a sheet light source, and a rotating code wheel which has at least one group pattern comprised of one pattern per presentation having discrete regions whose light transmission coefficients are selected to spatially modulate the light sheet into said coded light rays.

5. The system of claim 1 wherein said pattern generator and projector includes a sheet light source, a rotating code wheel which has one or more group patterns each comprised of one pattern per presentation having clear and opaque regions to spatially modulate the light sheet into said coded light rays, and a projection lens.

6. The system of claim 1 wherein said pattern generator and projector includes a sheet light source, a rotating code wheel which has at least one group pattern comprised of one pattern per presentation having discrete regions whose light transmission coefficients are selected to spatially modulate the light sheet into said coded light rays, a reduction lens to project said coded rays onto the entrance of a coherent optical fiber bundle, and a projection lens to reimage said coded rays on the object surface.

7. The system of claim 1 wherein said pattern generator and projector includes a narrow laser beam source, a modulator to programmably vary the intensity of said laser beam, and a beam deflector to scan the modulated beam along a straight line and project it onto the object surface.

8. A three-dimensional range camera comprising:

a pattern generator and projector to produce a 1×

N array of time and space coded light rays which can each be varied with time and to project P sequential presentations of different subsets of said light rays onto a three-dimensional object, where P=1+log₂ N and N is the number of light rays;

means for orthogonally sweeping said array of coded light rays by steps over a rectangular plane;

a linear array, line scan camera to image points of light on the surface of said object where said light rays are incident, and generate after each presentation a one-dimensional scan signal which has ray peaks at locations corresponding to imaged light points, said line scan camera generating a set of said scan signals per step; and

a range processor to analyze said scan signals, set by set, to uniquely identify all rays, determine depth from the displacement of said ray peaks from calibration, reference plane peaks, and output area range map data.

9. The range camera of claim 8 wherein said pattern generator includes a collimated light sheet source and a rotating code wheel which has group patterns each comprised of one pattern per presentation of discrete regions whose light transmission coefficients are selected to spatially modulate the light sheet into said coded light rays, said patterns being illuminated one at a time in sequence.

10. The range camera of claim 9 wherein said projector is a projection lens and said orthogonal sweep means is a rotating mirror.

11. The range camera of claim 8 wherein said pattern generator includes a sheet light laser source and a rotating code wheel which has sector-shaped group patterns each comprised of one pattern per presentation of clear and opaque regions to spatially modulate the light sheet into said coded light rays, said patterns being illuminated one at a time in sequence.

12. The range camera of claim 11 wherein said projector is comprised of a reduction lens to project said coded light rays onto the entrance of a coherent optical fiber bundle and a projection lens to reimage said coded rays on the object surface.

13. A range camera for profiling applications comprising:

a narrow laser beam source;

a modulator to vary the intensity of said laser beam;

a beam deflector to scan the modulated beam along a straight line and project it onto the surface of an object;

said modulator and beam deflector producing a 1×

N array of time and space coded light rays and P sequential presentations of different subsets of said light rays, where P=1+log_b N, b is the number of brightness levels and N is the number of light rays;

a linear array, line scan camera to image points of light on the surface of said object where said light rays are incident, and generate a one-dimensional scan signal which has ray peaks at locations corresponding to imaged light; and

a range processor to analyze said scan signals to uniquely identify all rays, determine depth from the displacement of said ray peaks from calibration, reference plane peaks, and output profile data.

14. The range camera of claim 13 wherein said modulator and beam deflector are controlled by said range processor.